1. Technical Field
The present invention relates to recording-medium-residual-quantity detecting devices that detect the residual quantity of a recording medium and are included in recording apparatuses, to which the invention also relates, that perform recording by feeding the recording medium from a roll in which the recording medium is wound. The invention also relates to liquid ejecting apparatuses.
Herein, liquid ejecting apparatuses are not limited to recording apparatuses such as printers, copiers, and facsimiles that include an ink jet recording head and perform recording on a recording medium by ejecting ink from the recording head. Liquid ejecting apparatuses include apparatuses that cause a liquid ejecting head, an equivalent of the ink jet recording head, to eject liquid, a material suitable for the required use instead of ink, toward an ejection target, an equivalent of the recording medium, so that the liquid adheres to the ejection target.
Examples of the liquid ejecting head other than the recording head include colorant ejecting heads used in manufacturing color filters of liquid crystal displays, electrode-material (conductive-paste) ejecting heads used in forming electrodes of organic electroluminescence (EL) displays and surface-emitting displays (field emission displays abbreviated as FEDs), bioorganic-material ejecting heads used in manufacturing biochips, and sample ejecting heads used as precision pipettes.
2. Related Art
In a printer used with roll paper, unless the residual quantity of the roll paper is known accurately, recording may be started despite there being insufficient residual quantity of the roll paper. In such a case, ink or the like may be wasted. Therefore, in a printer used with roll paper, it is critical to accurately know the residual quantity of the roll paper.
In the known art such as that disclosed in JP-A-5-16499, the residual quantity of roll paper is calculated by calculating the diameter of the roll paper from the difference between the number of rotations of a paper transporting roller and the number of rotations of the roll paper, the numbers being detected by corresponding detectors.
However, in the case where the residual quantity of roll paper is calculated while the transportation of the roll paper is initiated by a paper transporting roller, the roll paper is pulled by the paper transporting roller from the roll. In addition to this, transportation loads are applied to the roll paper in both the upstream and downstream portions of a transportation path with respect to the paper transporting roller. These three loads all act in a direction in which the roll paper tends to slip on the paper transporting roller, thereby easily causing slippage of the roll paper on the paper transporting roller. Consequently, the calculated residual quantity of the roll paper may contain an error.
However, if a dedicated detection roller that is caused to rotate by being in contact with the roll paper is provided for prevention of paper slippage, the complexity and the cost of the apparatus unpreferably increases.